Summary The MD helicopter 369D, serial number 370093D, was returning to Lake Cowichan, British Columbia, at about 1725 local time. The pilot had spent the day transporting cedar shake blocks in the Jordan River area. At about 1800 the helicopter was reported missing, and a search was begun at about 1845. An emergency locator transmitter signal was detected in the Mt.Modeste area. During the night, a ground search party found the destroyed helicopter, minus its tail. The pilot, who was the sole occupant, was in the wreckage and had been fatally injured. No fire had occurred. Ce rapport est galement disponible en franais. Other Factual Information On the day of the accident, the pilot flew the helicopter to the Jordan River area to spend the day transporting cedar shake blocks. The weather was mostly clear, allowing for visual flight rules (VFR) flight, and the winds were light and variable. Sunset was at 1655 Pacific standard time (PST),(1) and it turned dark at 1728. That day the pilot flew 4.9 hours, making 123 lifts, and transported the ground crews three times. At about 1715 he departed Jordan River for the 23-minute flight back to Lake Cowichan. He had filed a flight plan in the morning for the day's flying. The flight plan was to be closed by 1745, but since it was not, a search was initiated one hour later. The emergency locator transmitter activated when the helicopter collided with terrain. The crew of a Canadian Armed Forces search-and-rescue aircraft found the area of the downed helicopter and helped a ground search team find the main wreckage. The tail section had broken away from the helicopter and was found two days later, about one kilometre behind the main wreckage. The terrain of the accident site is mountainous, with second-growth trees and large areas that had been logged in the past 20 years. The helicopter struck the ground in a left-bank, nose-down attitude. Pieces of the helicopter and its contents were scattered around the main wreckage, up to 500 feet away. The fuselage was severely crushed by the high impact forces and was skewered by two small trees. Only one other tree in the area was damaged by the falling helicopter. The fuel cell had burst on impact, and there was a strong smell of fuel, but no fire had occurred. Figure 1 -Main rotor blade break Marks on the aft fuselage showed that the main rotor blades had severed the tail section. All of the lead and lag blade dampers were torn apart. The helicopter is fitted with five main-rotor blades that are identified by colour. The red blade was notable in that it showed a clean break about one-third of the distance from its root (see Figure 1). The break was perpendicular to the leading edge of the blade, and the break in the spar was recessed from the skin. The outboard two-thirds of this blade was not found. The white blade was missing completely, including its main-rotor blade grip. The yellow blade was missing its end one-third and showed clear damage from hitting the tail section. The green blade was torn into two pieces after it had stopped turning. The blue blade was the only blade in one piece. Apart from the damage caused by the blades striking the aft section of the fuselage in flight, the damage to the main-rotor system and the blades was consistent with that exhibited when the rotor is not turning or being driven at ground impact. Figure 2 - Detailed break of rotor blade break The red blade, with the clean break, was removed from the wreckage and transported to an independent engineering facility for examination. Detailed visual and scanning-electron microscope inspections revealed a bonding void between the blade skin and the spar. It also revealed corrosion pits in the spar, in the area of the bonding void. A fatigue crack had propagated from one of the pits and through the spar until the weakened blade failed from overload. The corrosion pit revealed chlorine and sulphur, as happens when the corrosion is from a marine or industrial environment. The manufacturer of the main-rotor blades was an approved parts manufacturer for main-rotor blades for the 369D. Early manufacturing of these blades included a process of checking for voids in bonding by monitoring for an uninterrupted squeeze-out of bonding material. In 1999 this check was supplemented by a tap inspection. Tap inspections are done by tapping the surface of the blade with a metal object, often a coin, and listening for a change in tone to identify voids. (Criteria have been established for acceptable voids.) The main-rotor blade with the clean break was manufactured before 1999. The pilot was the chief pilot of Prism Helicopters Ltd. He held a private aeroplane licence and a commercial helicopter licence. He was appropriately certificated and had a flight medical examination on 2 August 2000. This examination, like previous ones, showed that he was in good health. He had about 5800 hours of flying time, most of which was in the 369D. The helicopter was maintained in accordance with the manufacturer's, Transport Canada's, and the company's criteria. There were no outstanding deficiencies recorded. Four of the main-rotor blades, including the blade that failed, had accumulated about 2658 hours of flight time each. One blade had about 673 hours. The life limit of the main-rotor blades was 3530 hours. The helicopter manufacturer reported that the tail section could break under extreme vibrations, as would occur if a rotor blade or blade section was lost in flight.